1. Field of the Invention
The present invention relates to a method for fabricating a CMOS image sensor.
2. Discussion of the Related Art
Referring to FIGS. 1A and 1B, illustrating a CMOS image sensor, a metal line 1a is formed on a sub-layer 1, and then an etching process is performed to form a pad open. Subsequently, a pad layer 2 is formed on the sub-layer 1, and then a color filter array 3 is formed on the pad layer 2. A planar layer 4 is then formed on the color filter array 3, and a microlens 6 is formed.
The microlens 6 is formed with a reflow process using a photoresist 5 formed on the planar layer 4. However, a pad aluminum portion 2a, which is opened as shown in FIG. 1A, may be contaminated when performing a photo process. As such, the contaminated portion becomes a particle source.
When fabricating the CMOS image sensor, the final processing steps are related to the processes for forming the color filter array and the microlens. As explained above, the microlens are formed with the reflow method utilizing a photoresist.
However, this reflow method has difficulty forming a curved surface. As the size of microlens decreases, the radius of microlens also decreases. Thus, the height of microlens must be lowered, which can be difficult with the reflow method utilizing the photoresist.